1. Field of the Invention
The present invention relates to an automotive seat in which only seat cushion is raised and lowered by a lifter while a seat back is fixed at a constant height.
2. Description of the Prior Art
Conventionally, there is known a seat cushion with a lifter which is adapted to raise and lower the seat cushion with respect to a seat back so as to adjust the height of an occupant's viewpoint or according to the occupant's body condition. In this type of seat cushion, as shown in FIG. 1, the seat back (21) is fixedly secured to a bracket (31) welded to a slide rail (22) and only the seat cushion (12) is raised and lowered by the lifter. For this reason, the lower position of the seat cushion (12) is set at a position which is spaced away from the seat back (21) by the maximum raising/lowering distance (stroke) of the seat cushion (12). And, a spacing (10) between the seat back (21) and the seat cushion (12), in more detail, the spacing (10) between the lower end of the seat back (21) and the rear end upper surface of the seat cushion (12) can be varied as the seat cushion (12) is raised or lowered.
The existence of the spacing (10) between the seat back (21) and the seat cushion (12) worsens the appearance of the seat as well as gives the occupant such an impression that the seat is not of fine quality. In view of this, there have been proposed a large number of seats with a lifter each of which is adapted to always close or cover such spacing (10).
Now, the lifter shown in FIGS. 1 and 2 is adapted to raise or lower the front and rear portions of the seat cushion (12) indepently of each other. Specifically, in this type of lifter, if an operation handle (32) with an anti-reversal device provided on the outside of the bracket (31) is rotated, then a pinion gear (33), which is fixed to the shaft of the operation handle (32) and disposed inside of the bracket (31), is rotated and thus a rack (34) intermeshing with the pinion gear (33) is pushed or pulled in the direction of a shown arrow, with the result that a V-shaped link (36) rotatably mounted to a shaft (35) extending across the right and left brackets (31) is rotated to thereby raise or lower the rear portion of the seat cushion (12). Also, if another operation handle (37) with an anti-reversal device is rotated, then a pinion gear (38), which is formed integrally with the shaft of the operation handle (37) and disposed inside of the brackets (31), is rotated and thus a sector-shaped gear plate (39) intermeshing with the pinion gear (38) is also rotated, so that a torque shaft (41) mounted integrally with the sector shaped gear plate (39) is rotated. Due to the rotaional movement of the torque shaft (41), a link (40) having one end welded to the torque shaft (41) is rotated to raise or lower a leg piece member (42) of the seat cushion (12) to which the other end of the link (40) is mounted, thereby raising or lowering the front portion of the seat cushion (12).
As the seat cushion with a lifter for covering the above-mentioned spacing, there is well known a structure in which a sheet is provided so as to extend between a seat cushion and a seat back. As an example of this type, there can be pointed out a structure which is disclosed in Japanese Utility Model Publication No. 53-60224. In the disclosed structure, there is provided a flexible sheet between the rear end portion of the seat cushion and the lower end of the seat back. This is a simple structure and, still more, with such structure, the spacing between the seat back and the seat cushion can be always closed.
Also, there is known another structure in which no sheet is used, but the expansion or contraction of a resilent body is used to close the above-mentioned spacing. As an example of this type, there can be shown a structure which is disclosed in Japanese Utility Model No. 60-115731. According to this structure, a resilient body is embedded into a top cover member, for example, at the lower end of a seat back or on the rear end upper surface of a seat cushion and the resilient body can be expanded or contracted freely to close the spacing. Alternatively, the resilient body is stored into a bag-shaped member and by hanging down the bag-shaped member from the lower end of the seat back or by disposing the bag-shaped member on the rear end surface of the seat cushion the spacing can be closed.
However, in the above-mentioned prior art structure using the sheet to close the spacing, when the seat cushion is raised or lowered fully, the sheet is caused to hang down backwardly, which may damage the appearance of the seat. Also, it is true that such structure offers no problem in function, but, due to the fact that the sheet is simply stretched, it lacks in a qualitative and quantitative feeling as well as in a weight feeling, that is, it is disadvantageous in that it lacks in a high-quality feeling.
Also, in the above-mentioned prior art structure in which the resilient body is stored in the bag-shaped member and the bag-shaped member is suspended down from the lower end of the seat back or the bag-shaped member is disposed on the rear end surface of the seat cushion, the bag-shaped member is located not internally but externally of the top cover member, which is not preferred in the sense of the quality of the appearance of the seat. Further, in this type of structure, due to its dependence on the use of the natural hanging-down and rising of the bag-shaped member to store the resilient body therein, it is difficult to close the spacing securely, and, in some cases, the spacing may be left unclosed. On the other hand, in the above-mentioned prior art structure in which the resilient is embedded into the seat back or seat cushion, the spacing can be securely closed. The last mentioned structure also offers no problems in the sense of the appearance quality, qualitative and quantitative feeling and weight feeling but it provides the highquality feeling.
In addition, in the above-mentioned prior art structures there is found another problem that the lifter disposed below the seat cushion can be seen from behind, which is disadvantageous in view of the apperance quality of the seat. However, in the above-mentioned well known structures including the structure in which the resilient body is embedded into the seat back or seat cushion, no attention is paid to this problem. That is, in all of the above-mentioned prior art structures, the lifter is not covered but exposed.